1. Field of the Invention
The present invention relates to a dynamic random access memory or in particular to test of dynamic random access memories.
2. Description of the Prior Art
A dynamic random access memory comprises a plurality of circuit portions for processing address, data and control signals as well as a memory cell for storing data. An internal voltage generator generates internal voltages such as a cell plate potential, a precharge voltage for bit lines or a substrate voltage from a power supply voltage applied from the external, and the internal voltages are supplied to operate the dynamic random access memory.
Because internal voltages are generated from the external supply voltage, they change with the power supply voltage. Then, it is desirable that circuit portions receiving internal voltages in a dynamic random access memory operate stably against variation of power supply voltage. However, there are products which are liable to operate abnormally against such variation. It has to be prevented to forward defective products having a narrow operation range dependent on internal voltage. However, defective products may not be checked if input signals are provided to input pins of dynamic random access memories to observe response at output pins.